Vaccination against Staphylococcus aureus experimental endocarditis using recombinant Lactococcus lactis expressing...

Area of Science:

• Microbiology
• Immunology
• Vaccinology

Background:

• Staphylococcus aureus is a significant pathogen causing severe human and animal infections, necessitating vaccine development.
• Lactococcus lactis, a non-pathogenic bacterium, serves as a potential vector for delivering antigens for vaccination.

Purpose of the Study:

• To evaluate the efficacy of non-living Lactococcus lactis heterologously expressing Staphylococcus aureus antigens (clumping factor A [ClfA] and fibronectin-binding protein A [FnbpA]) in eliciting immune responses and protecting against experimental infective endocarditis (IE) in rats.

Main Methods:

• Rats were immunized with non-living Lactococcus lactis engineered to express S. aureus ClfA, FnbpA, or both.
• Immune responses were assessed by measuring antibody production and cytokine profiles (IL-17A).
• Protection against S. aureus IE was evaluated using experimental infection models with S. aureus strains Newman and P8.

Main Results:

• Vaccination with L. lactis ClfA induced antibodies that inhibited S. aureus Newman binding to fibrinogen, promoted IL-17A production, and protected 68% of rats from IE.
• Immunization with L. lactis expressing FnbpA (alone or with ClfA) generated antibodies but did not prevent S. aureus P8 binding to fibrinogen or fibronectin, nor did it protect against IE.
• Constructs containing FnbpA did not enhance IL-17A production.

Conclusions:

• Lactococcus lactis is a viable antigen delivery system capable of inducing robust humoral and cellular immune responses.
• While L. lactis ClfA demonstrated protective potential against S. aureus IE, further investigation is required to identify the most effective antigens for a comprehensive S. aureus vaccine.